You need to service your buffer tank and replace the wire. This kind of problem generally occurs when there is not uniform current flowing through the wire. It could also be possible that the wire is misplaced from the left end. If you are using smaller gel cassette in bigger tank, they to place the cassette in the middle from both the sides, this will ensure uniform force across the gel.

Dear, its normal situation

Typically, the movement starts from the cathode to the positive electrode

So one of them moves and separates and the other does not

You can get this effect by pouring the agarose too hot into the gel tray. The tray warps and the comb comes too close to the floor of the gel tray so when you remove the comb it breaks the gel. The sample runs through the hole so there is little left to run. Next time you pour a gel clean the comb thoroughly and load running dye in the end position and watch to see if the colour runs under the gel. If this is not the case then I think @Abhijeet Singh is right